The “thrifty genotype” of Britain’s native pony breeds may put them at greater risk of obesity, according to researchers who have shone a spotlight on Britain’s paddock potatoes.

They say equine obesity is an increasing but under-recognised welfare issue in Britain.

Their conclusions are supported by new research from the Animal Health Trust recently published in the Equine Veterinary Journal.

Data collected from 785 horses and ponies – 31 percent of which were classified as obese – over a two-year period between 2009 and 2011, has been used to explore various elements that contribute to the risk of obesity in British horses and ponies.

The research, funded by World Horse Welfare, identified several factors which may increase the risk of being obese.

Pony breeds, particularly British native breeds and heavier horses such as draught and cob types, were all significantly more likely to be obese compared to thoroughbreds. The increased risk may be due to these native breeds having adapted to thrive in harsh environments with sparse grazing available.

“Native breeds may be genetically better adapted to survive in harsh conditions, having a so-called thrifty genotype, increasing their risk of obesity when maintained in an environment where food is of better quality and more readily available,” said Animal Health Trust research assistant Charlotte Robin, who was lead author of the paper.

Horses described by their owners as readily being able to gain weight or being “good doers” were more than three times more likely to be obese, compared to those that normally maintained weight.

The research also highlighted various links to human obesity.

“In humans, obesity is associated with poor health status and chronic health conditions including diabetes, hypertension, respiratory disease and arthritis. Similar associations between obesity and adverse health events have been described in equines,” Robin said.

Rhia pops on the scales for the bad news. Photo: World Horse Welfare

Similarly in humans, exercise significantly improves insulin sensitivity, and it is thought the same “dose-response” effect is mirrored in horses.

The research shows that the risk of obesity is greater in pleasure or non-ridden horses, with pleasure horses being more than twice as likely to be obese and non-ridden horses being nearly three times more likely to be obese.

Competition animals will receive increased exercise at a higher intensity and be fitter than non-competition animals, further reducing the risk of obesity.

“Competition horses are likely to be managed in different ways compared to non-competition or non-ridden animals and this may also contribute to the reduced risk of obesity within this sub-population,” Robin said.

World Horse Welfare’s deputy head of British support, Sam Chubbock, said excess weight was one of the greatest challenges facing horse owners in Britain today, which was why the charity supported the research.

“Being overweight can be just as much, if not more, of a health concern as being underweight.

“In our experience it can take three times longer to get an overweight horse back to optimum condition than it can a thin horse. Moreover, a previously obese horse’s weight will need to be managed for the rest of its life, even after the weight has come off, and they are likely to suffer long-term effects.

“Managing a horse prone to weight gain can be incredibly difficult and this is why our Right Weight project provides practical guidance for owners on how to assess and manage their own horse’s weight.”

One of the most common health conditions linked to equine obesity is laminitis. A new Animal Health Trust study, in collaboration with the Royal Veterinary College and also backed by World Horse Welfare, aims to take a closer look at the management factors which may increase the risk of laminitis in the British equine population.

The study, launching this month, will ask owners of laminitic and non-laminitic horses or ponies to complete monthly online diaries.

The trust’s obesity research has helped to highlight obesity as a significant equine welfare issue. People frequently misclassify their own weight or body shape, and this phenomenon also applies to perceptions about our pets’ weight.

Research has shown that dog and horse owners tend to underestimate their animals’ weight, suggesting the prevalence of obesity in the study is likely to be an underestimation.

Robin explains: “It is possible that in certain breeds, being overweight or obese has been normalised to a certain extent. Owners may find it easier to identify an overweight thoroughbred, compared to an overweight cob or native pony.

“Helping owners identify when their horse is overweight or obese is an essential aspect of reducing the welfare impact of equine obesity.”